"The latest reports said that up to 35 security members were killed in yesterday clashes in the village of al-Dulaimat, some 30km south of Baquba, the capital city of Diyala," the source told Xinhua on condition of anonymity.

He said that 27 policemen and eight Awakening Councils fighters were killed in the battle which broke out at about 3:30 p.m.(1230 GMT) when suspected al-Qaida militants ambushed the joint force during an operation in the village seeking al-Qaida suspects, the source said.

Earlier, the source said 20 policemen, including two senior officers, and eight Awakening Council fighters were killed in the ambush.

The source could not tell how many suspected al-Qaida militants were killed by the fierce clashes.

Diyala has been the hotbed of terrorist operations since the U.S.-led invasion of Iraq in 2003, teeming with bombings and other types of attacks.

The U.S. military and the Iraqi troops have launched multiple major operations in the region.

The security situation in Iraq has gradually improved since late 2007, mainly thanks to a surge of U.S. troops, ceasefire of a major Shiite militia, and the uprising of Iraqi Sunnis, the major part of the Awakening Council, against al-Qaida.